In an independently control-type air conditioning apparatus for independently controlling the air temperatures of left and right areas of a passenger compartment of a vehicle, a space inside of an air conditioning case is generally separated into two air passage spaces, and air mixing doors are respectively provided in the two air passage spaces. The air mixing doors are independently operated such that the temperatures of air in the two air passage spaces are separately controlled. As such, the temperatures of air to be blown toward the left and right areas of the passenger compartment are differentiated.
In fact, to improve efficiency of designing and manufacturing air conditioning apparatuses, it is preferable to share component parts between the independently control-type air conditioning apparatus and a general control-type air conditioning apparatus that does not independently control the air temperatures of the left and right areas. For example, Japanese Unexamined Patent Publication No. 11-48746 discloses air mixing doors that can be used in both of the independently control-type air conditioning apparatus and the general control-type air conditioning apparatus.
For example, as shown in FIG. 9, a shaft receiving member 80 is provided between a first rotation shaft 131a of a first air mixing door 131 and a second rotation shaft 132a of a second air mixing door 132. The shaft receiving member 80 includes a rotational portion 81, a first shaft receiving portion 82 extending from the rotational portion 81 and a second shaft receiving portion 83 extending from the rotational portion 81 in a direction opposite to the first shaft receiving portion 81. The shaft receiving member 80 is rotatably supported by the separation wall through the rotational portion 81.
The first and second shaft receiving portions 82, 83 are engageable with engaging holes 84, 85 of the first and second rotation shafts 131a, 132a. The first shaft receiving portion 82 and the second shaft receiving portions 83 respectively have a first projection 82a and a second projection 83a as rotation -restricting portions. An axial length of the first projection 82a is longer than that of the second projection 83a. 
The engaging hole 84 of the first rotation shaft 131a is configured to receive the first shaft receiving portion 82 and the second shaft receiving portion 83 in a rotation restricted manner for restricting rotation of the shaft receiving member 80 relative to the first rotation shaft 131a. On the other hand, the engaging hole 85 of the second rotation shaft 132a is configured to rotatably receive the second shaft receiving portion 83 but to receive the first shaft receiving portion 82 in the rotation restricted manner.
When the shaft receiving member 80 is assembled in a first assembled condition where the first shaft receiving portion 82 is engaged with the engaging hole 84 of the first rotation shaft 131a and the second shaft receiving portion 83 is received in the engaging hole 85 of the second rotation shaft 132a, the first rotation shaft 131a is not rotatable relative to the shaft receiving member 80, but the second rotation shaft 132a is rotatable relative to the shaft receiving member 80.
On the other hand, when the shaft receiving member 80 is assembled in a second assembled condition where the second shaft receiving portion 83 is engaged with the engaging hole 84 of the first rotation shaft 131a and the first shaft receiving portion 82 is engaged with the engaging hole 85 of the second rotation shaft 132a, the first and second rotation shafts 131a, 132a are not rotatable relative to the shaft receiving portion 80.
Namely, in the first assembled condition, the first and second air mixing doors 131, 132 are rotatable independently from each other. In the second assembled condition, the first and second air mixing doors 131, 132 are rotatable together. As such, the first and second air mixing doors 131, 132 are used for both of the independent control-type air conditioning apparatus and the general control-type air conditioning apparatus.
In this case, however, the shaft receiving member 80 is required as an individual member. Also, the engaging holes 84, 85 of the first and second rotation shafts 131, 132 have different shapes. That is, the first and second air mixing doors 131, 132 are different components. Accordingly, the number and types of components increase, resulting an increase in costs.